This invention relates to apparatus for forming heat sealed articles from a strip of two superimposed layers of heat sealable material.
British Pat. Specification Nos. 815,006 and 1,054,644 both disclose apparatus for forming heat sealed articles from a zig-zag strip of two superimposed layers of heat sealable material. In both these specifications the strip is supported on one side only of the zig-zag and several heating sources are provided to engage the strip at the transverse crests along that side of the strip. A severe disadvantage of such an arrangement is that it is extremely difficult to maintain all the sources at an even temperature with the result that different amounts of heat are supplied at the locations to be welded resulting in uneven welding conditions along the strip. Furthermore, the clamping arrangements disclosed in these patents which only support the strip along one side of the zig-zag require either heating elements located on the ends of radial arms of the central support structure, or a series of heaters located on an endless belt. Both of these arrangements are extremely complicated as well as having the uneven heat supply mentioned above.
It is an object of the invention to overcome these disadvantages and in particular to provide an apparatus in which a simplified heat sealing arrangement is provided.